Tutorial by Examples: nd

ob_start is especially handy when you have redirections on your page. For example, the following code won't work: Hello! <?php header("Location: somepage.php"); ?> The error that will be given is something like: headers already sent by <xxx> on line <xxx>. In or...

This book is known as CLtL2. This is the second edition of the book Common Lisp the Language. It was published in 1990, before the ANSI CL standard was final. It took the original language definition from the first edition (published in 1984) and described all changes in the standardization process...

When PyInstaller is used without any options to bundle myscript.py , the default output is a single folder (named myscript) containing an executable named myscript (myscript.exe in windows) along with all the necessary dependencies. The app can be distributed by compressing the folder into a zip fi...

pyinstaller myscript.py -F The options to generate a single file are -F or --onefile. This bundles the program into a single myscript.exe file. Single file executable are slower than the one-folder bundle. They are also harder to debug.

For the sake of this example, it is assumed the user is running Jetty as a distribution. For information on how to run Jetty as an embedded web server, please refer to the official documentation. Jetty can be downloaded from here and is available in both .zip and .gzip formats. Current versions of ...

On CLiki, a Wiki for Common Lisp and free Common Lisp software, a list of Proposed ANSI Revisions and Clarifications is being maintained. Since the Common Lisp standard has not changed since 1994, users have found several problems with the specification document. These are documented on the CLiki p...

There are several good examples of using lambdas as a FunctionalInterface in simple scenarios. A fairly common use case that can be improved by lambdas is what is called the Execute-Around pattern. In this pattern, you have a set of standard setup/teardown code that is needed for multiple scenarios ...

When to use Virtually all WPF controls make heavy use of dependency properties. A dependency property allows for the use of many WPF features that are not possible with standard CLR properties alone, including but not limited to support for styles, animations, data binding, value inheritance, and c...

When to use An attached property is a dependency property that can be applied to any DependencyObject to enhance the behavior of various controls or services that are aware of the property's existence. Some use cases for attached properties include: Having a parent element iterate through its c...

When to use A read-only dependency property is similar to a normal dependency property, but it is structured to not allow having its value set from outside the control. This works well if you have a property that is purely informational for consumers, e.g. IsMouseOver or IsKeyboardFocusWithin. How...

Generic parameters can also be bound to more than one type using the T extends Type1 & Type2 & ... syntax. Let's say you want to create a class whose Generic type should implement both Flushable and Closeable, you can write class ExampleClass<T extends Flushable & Closeable> { }...

To make a class a subclass of another class, use parent pragma: package Point; use strict; ... 1; package Point2D; use strict; use parent qw(Point); ... 1; package Point3D; use strict; use parent qw(Point); ... 1; Perl allows for multiple inheritance: package Point2D; use stri...

In Perl, the difference between class (static) and object (instance) methods is not so strong as in some other languages, but it still exists. The left operand of the arrow operator -> becomes the first argument of the method to be called. It may be either a string: # the first argument of new ...

This will create a composite index of both keys, mystring and mydatetime and speed up queries with both columns in the WHERE clause. CREATE INDEX idx_mycol_myothercol ON my_table(mycol, myothercol) Note: The order is important! If the search query does not include both columns in the WHERE claus...

Collections in Java only work for objects. I.e. there is no Map<int, int> in Java. Instead, primitive values need to be boxed into objects, as in Map<Integer, Integer>. Java auto-boxing will enable transparent use of these collections: Map<Integer, Integer> map = new HashMap<&g...

redis-cli is the Redis command line interface program that allows to send commands to Redis and read the replies sent by the server, directly from the terminal. Basic command line usage is below: Access to redis: $ redis-cli 127.0.0.1:6379> Access to redis with authentication: $ redis-cli ...

The trim() method returns a new String with the leading and trailing whitespace removed. String s = new String(" Hello World!! "); String t = s.trim(); // t = "Hello World!!" If you trim a String that doesn't have any whitespace to remove, you will be returned the same S...

Mercurial makes it easy to share your work, and to pull in contributions from other developers. This involves three key steps; cloning, pulling, and pushing. Clone To copy a remote repository to your local disk you "clone" it. To do so simply pass the remote URL you'd like to clone from....

Panels can have sections, sections can have settings, and settings can have controls. Settings are saved in the database, while the controls for particular settings are only used to display their corresponding setting to the user. This code creates a basic section in the panel from above. Inside a...

Rails is shipped by default with ActiveRecord, an ORM (Object Relational Mapping) derived from the pattern with the same name. As an ORM, it is built to handle relational-mapping, and more precisely by handling SQL requests for you, hence the limitation to SQL databases only. However, you can stil...